Another amateur discovery was made on Dec. 28, 2002, by the American Charles W. Juels and the Brasilian Paulo R. Holvorcem, who maintain a close collaboration via the Internet concerning observation and data reduction of minor planets and comets. The discovery was made - the first night with this special equipment! - with a 12cm-refractor, equipped with a CCD camera, yielding a field of 2.3 x 2.3°. The comet appeared as a 15.1m object with a 1.8' coma in the constellation Coma Berenices. Further observations showed a 2.5' coma with a 30" inner coma (IAUC 8039). The comet passed perihelion in mid-April 2003, but was not expected to get brighter than 10-11m.
Yet the comet showed a steep brightness increase during the first weeks, which would have resulted in a maximum brightness of 4.5m and a maximum visual tail length of 2.5°, if this evolution would have continued until perihelion. However, the probability was high that this comet would experience a sudden drop in activity on its way to perihelion, resulting in a maximum brightness of only 5-6m.
This suggestion became reality; around Mar. 2 the activity dropped significantly. The following analysis is based on 56 observations by 8 members of the German Comet Section and 340 international ones (until the end of August). This data base clearly shows a significant change of the brightness evolution 42 days before perihelion. As a consequence the maximum brightness did not reach 4.5m, but only 6.4m. After perihelion it could be further followed from the southern hemisphere and showed a continuous decline in brightness, which however, can only be simulated properly with a dt-based formula.
Heliocentric brightness (pre-perihelion)
Total Brightness and Coma diameter
The apparent coma diameter increased from 2' (150.000 km) at the start of January 2003 to about 13' (550.000 km) shortly after the comet reached its minimum distance to the earth (0.892 AU on Feb. 16). On its way toward perihelion it decreased to about 4' (ca. 220.000 km). After perihelion the coma increased - due to the diminishing solar wind - from 4' (280.000 km) to 6' (400.000 km) in mid-June. Thereafter it decreased to 1' (100.000 km) until end of August. The degree of condensation was equivalent to DC 2-3 at the beginning of the apparition. During the following weeks it increased - slowly at first, but accelerating with time - and approached DC 8 at perihelion. After perihelion the degree of condensation decreased continuously from DC 7-8 to DC 3 at the end of July.
Visual tail sightings date from mid-February to the beginning of April. The maximum visual tail length was reported during the very last days of March. Thereafter low altitude and interference from twilight did not allow an observer to discern the tail in its whole extent. The maximum visual tail length reported was 1° (5 Mill. km). During most of the apparition the tail pointed approximately towards north. No tail sightings have been reported after perihelion.
Andreas Kammerer
